The other day my dad sent me a link to Lulu.com. It's an online publishing site which will sell your book for you, but only print it as and when people need a copy, so you don't need to lay out a ton of cash. It can even get you onto other online bookshops such as Amazon.
The other cool thing Lulu does is print up copies of your book for a non-exorbitant fee. If you can get over the idea that you are dipping a toe in the waters of vanity publishing, getting your own book physically made up for £7 each has a few valuable benefits:
First, if you feel your book is 'finished' (of course, it's never finished) then you might want someone outside the publishing business to read it. Such people probably don't want 500 pages of single-sided, double-spaced A4. They might want to read your book in the bath or on a train and would therefore be less than keen to lug such a big pile of ex-tree wherever they go. So for £7 you can get around this problem and give them an easy book-sized book to read.
Second, you can add your own image designs and cover blurb. This can have the same effect as a movie trailer, in that it puts the reader in the right frame of mind for the coming tale. Much better than a big white page with a few words written in Courier or American Typewriter.
Third, you get to see your book as a book. After all the time it's taken to create the bloody thing, it's quite a pleasant and encouraging experience to see it as it ought to be. It also helps to judge the way it feels when you pick it up and flick through it. Does it seem right? Do the chapters follow one another properly? Does it have too much white space? Not enough? Would you read it if you hadn't written it? You can now peruse it in a book-reading mind set that might help you judge it better.
For all that, Lulu is relatively inexpensive, and I haven't even mentioned the sad little thrill you get from having a UPS box arrive with your books (I ordered seven) as if you've actually been published.
It's kind of like Diet Coke versus The Real Thing, and it'll do for now.